[SOLVED] System fan and case fans

[inkisblood]

I have a question regarding my system fan. And another regarding case fans.

System: Ryzen 3 1200, 16gb RAM (DDR4 2666mhz), Radeon RX550 (4gb), MSI A320-PRO M2 motherboard, and RAIDMAX RX-400 XT PSU. I’m running a Linux OS: UBUNTU 21.10.


According to the literature, the PSU has a “smart thermal fan speed control circuit”, but there isn’t a connector to attach it to the “system fan control” header on the motherboard. The system fan seems fine, though it runs continuously, and doesn’t register in the BIOS.


My question is: if I get a Molex or Sata to 3 or 4-pin fan controller cable, will I then be able to use the BIOS fan controller settings? Or does it need to be a dedicated cable to make use of the PSU’s “fan speed control circuit”? Both PWM and Voltage control are available in the BIOS.


A second question regarding case fans: My local ambient temperature can get pretty high, so I want to add a couple of case fans. But the ones I have both have Molex connectors. They run at full speed from startup. I’d like to add these to the motherboard’s system fan control. What’s the best way to go about this? Will a splitter cable work? 2 x Molex to 3-pin fan controller for voltage control)? Or will I need separate cables and a whole fan controller unit? The latter seeming more likely if I also want the system fan to work?

Thanks for taking the time.

 

[JohnBonhamsGhost]

any power supply fan would be controlled and monitored by the PSU itself.
not based on user system temps, but by the PSU's internal temp.

molex or SATA powered fans cannot be controlled by the BIOS or motherboard control software.
they will only run at a static RPM.

you will need to purchase PWM fans and connect them to 4pin PWM headers on the motherboard for RPM control based on temperature.

it's also possible to use 3pin DC controlled fans but they usually also need to be connected to 4pin PWM headers and then setup as "DC" in BIOS.
but they will not offer the same amount of customization as true PWM fans.

 

[inkisblood]

any power supply fan would be controlled and monitored by the PSU itself.
not based on user system temps, but by the PSU's internal temp.

molex or SATA powered fans cannot be controlled by the BIOS or motherboard control software.
they will only run at a static RPM.

you will need to purchase PWM fans and connect them to 4pin PWM headers on the motherboard for RPM control based on temperature.

it's also possible to use 3pin DC controlled fans but they usually also need to be connected to 4pin PWM headers and then setup as "DC" in BIOS.
but they will not offer the same amount of customization as true PWM fans.

Thanks, JBG,

So, as I understand it now:The PSU fan is controlled by the PSU without any need to try and fiddle with it via BIOS or anything else?

And that there is no way to connect Molex case fans to the motherboard's 4-pin fan controller. Dedicated 3-pin (DC) or 4-pin (PWM) fans would be required for this?

Thanks. Very helpful.

 

[Paperdoc]

You CAN use an adapter to power your existing fans (with male Molex connectors on them) to your only mobo SYS_FAN header. You need this

https://www.amazon.com/3pin-power-4...26379&sprefix=fan+molex+adapter,aps,84&sr=8-8

NOTE that this one is made specifically for this purpose - it has a FEMALE standard 3-pin fan connector to plug into the male mobo SYS_FAN header, and a FEMALE 4-pin Molex connector (only 2 wires in use) so you can plug in a male Molex from your fan. You'd need two of these for your two fans, PLUS a simple Splitter with 2 (or more, if adding fans) output arms, like this

https://www.amazon.com/Splitter-Tea...41926801&sprefix=fan+splitter,aps,102&sr=8-10

That's a 2-pack of 4-pin Splitters with 4 outputs, and you can use one of them. Although it is a 4-pin Splitter, it can be used with 3-pin fans.

The fans you have are like older 3-pin fans in the sense that their speed can be altered only by changing the VOLTAGE supplied to them on Pins 1 and 2. They are different in that they do NOT have a speed signal output from Pin #3. So you CAN power them from your SYS_FAN header, AND control their speeds IF you configure that header to use the older DC Mode, rather than the newer PWM Mode (see mobo manual p. 13). However, since they cannot send any speed signal back to the header, that header MAY give you warnings that its fan has failed because it gets NO speed signal.

IF you add another fan(s) to those you have, get ONLY 3-pin older Voltage Controlled fans to mix with them. Mixing newer 4-pin PWM fans with them is not advised. If you do that, note on the SLITTER that only ONE output arm has all 4 pins in it. That is the only output that will send back to the host header the speed signal from its fan, and there is no such signal from your old fans. BUT you SHPOULD plug a new 3-pin added fan into that output becaue it WILL send a speed signal back that way and keep your SYS_FAN header happy.

Your other option, of course, it to do a JBG recommended: scrap the existing fans, and buy a set of new 4-pin PWM fans, use the Splitter to connect those to your SYS_FAN header, and configure that header to use PWM Mode.

 

[inkisblood]

You CAN use an adapter to power your existing fans (with male Molex connectors on them) to your only mobo SYS_FAN header. You need this

https://www.amazon.com/3pin-power-4pin-molex-adapter/dp/B000H25PBK/ref=sr_1_8?crid=3DFCPC4ERLVZ5&keywords=fan+molex+adapter&qid=1641926379&sprefix=fan+molex+adapter,aps,84&sr=8-8

NOTE that this one is made specifically for this purpose - it has a FEMALE standard 3-pin fan connector to plug into the male mobo SYS_FAN header, and a FEMALE 4-pin Molex connector (only 2 wires in use) so you can plug in a male Molex from your fan. You'd need two of these for your two fans, PLUS a simple Splitter with 2 (or more, if adding fans) output arms, like this

https://www.amazon.com/Splitter-TeamProfitcom-Computer-Extension-Converter/dp/B07TRV6XZX/ref=sr_1_10?crid=2NYRKP09MG3VN&keywords=fan+splitter&qid=1641926801&sprefix=fan+splitter,aps,102&sr=8-10

That's a 2-pack of 4-pin Splitters with 4 outputs, and you can use one of them. Although it is a 4-pin Splitter, it can be used with 3-pin fans.

The fans you have are like older 3-pin fans in the sense that their speed can be altered only by changing the VOLTAGE supplied to them on Pins 1 and 2. They are different in that they do NOT have a speed signal output from Pin #3. So you CAN power them from your SYS_FAN header, AND control their speeds IF you configure that header to use the older DC Mode, rather than the newer PWM Mode (see mobo manual p. 13). However, since they cannot send any speed signal back to the header, that header MAY give you warnings that its fan has failed because it gets NO speed signal.

IF you add another fan(s) to those you have, get ONLY 3-pin older Voltage Controlled fans to mix with them. Mixing newer 4-pin PWM fans with them is not advised. If you do that, note on the SLITTER that only ONE output arm has all 4 pins in it. That is the only output that will send back to the host header the speed signal from its fan, and there is no such signal from your old fans. BUT you SHPOULD plug a new 3-pin added fan into that output becaue it WILL send a speed signal back that way and keep your SYS_FAN header happy.

Your other option, of course, it to do a JBG recommended: scrap the existing fans, and buy a set of new 4-pin PWM fans, use the Splitter to connect those to your SYS_FAN header, and configure that header to use PWM Mode.

Thanks, Paperdoc, this was about to be my next query. I did have a look a PWM fans, but I'm in South Africa and supplies are limited for 80mm PWM, of which I need one for my rather clumsy midi case. Fortunately, both the cables you've mentioned I can get hold of.

I was concerned that the 2 pins of Molex wouldn't allow for old DC control.

Thanks for clearing that up. And thanks for the comprehensive response. This is probably the route I'll take.

 

[Paperdoc]

You're welcome, and good luck. Thanks for Best Solution.